Photothermographic substance



United States Patent PHOTOTHERMOGRAPHIC SUBSTANCE Marilyn Levy, RedBank, N. J., and Heinz Schulze, Binghamton, N. Y., assignors to theUnited States of America as represented by the Secretary of the Army NoDrawing. Original application June 29, 1954, Serial No. 440,308. Dividedand this application March 8, 1955, Serial No. 496,356

2 Claims. (Cl. 95-7) (Granted under Title 35, U. S. Code (1952), see.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes without the payment of anyroyalty thereon.

This invention relates to new photothermograp'hic substances and tophotographic layers sensitized with the new photothermographicsubstances.

The term photothermographic has been defined in U. S. Patent 2,095,839as characterizing a material which after its exposure to light may bedecomposed or modified by the action of heat difierentially inaccordance with the exposure to light. A photographic layer sensitizedwith such photothermographic substances is therefore, after exposure tolight, developable by heat.

The present invention is based on the discovery that the silver salt ofbenzamidoxime is a valuable thermographic substance which will produceafter exposure to light and subsequent to heat treatment a visiblerecord of the incident light.

The invention will become more apparent from the description of anembodiment of the broad inventive idea.

Preparation of the silver salt of benzamidoxime:

=NOH CsHsC --NHa Dissolve 2.72 grams of benzamidoxime in 50 ml. of Wateron a water bath. Cool to approximately 25 C. Dissolve separately 3.40grams AgNOa in m1. H20 and add 3 ml. ammonium hydroxide (26 B.) so thatany precipitate which may first form again dissolves; cool this secondsolution to 25 C. and dump it into the first solution. The precipitatenow formed is filtered and washed with 20 ml. of water to which 0.6 ml.NH3 (26 B.) was added. The precipitate was dried over night in a vacuumdesiccator over calcium chloride. The compound remains white after thisperiod of time but decomposes rapidly even if stored in the dark.

Since the silver benzamidoxime is decomposed by water, it was necessaryto disperse this salt in a vehicle of polystyrene dissolved in benzene.The mixture was coated on glass slides and dried over night in the dark.The slides were exposed to light and thermally developed at C.

The photothermographic substances according to the invention may bedispersed in any suitable colloidal carrier to produce aphotothermographic layer on one of the conventional supports. Thematerial for the photographic layer may consist of gelatin, casein,agar, and various natural or synthetic high polymers such as the alreadymentioned polystyrene or phenol formaldehyde resins, vinyl resins, alkydresins, etc. The support for the photographic layer may be a plate ofany of the commonly used materials such as glass, paper, cellulosederivatives, etc.

As described in the parent application Serial No.

440,308, filed June 29, 1954, of which this application is a division,the light sensitivity of the silver salt of benzamidoxime will depend,like in the case of the silver salts described in the parentapplication, (a) on the variation ratio of silver nitrate tobenzamidoxime, (b) on the type of gelatin used to disperse the silversalts, and (c) the variation in the ratio of silver salts to gelatin inthe emulsions.

It will be obvious to those skilled in the art that a great manyvariations and combinations of the described processes are possiblewithin the broad inventive idea as characterized in the appended claims.

What is claimed is:

l. A photothermographic element comprising a support and aphotothermographic layer comprising an organic colloid carrier havingdispersed therein the silver salt of benzamidoxime.

2. A photothermographic element comprising an organic colloid carrierhaving dispersed therein the silver salt of benzamidoxime.

References Cited in the file of this patent UNITED STATES PATENTS2,095,839 Sheppard et al Oct. 12, 1937

1. A PHOTOTHERMOGRAPHIC ELEMENT COMPRISING A SUPPORT AND A PHOTOETHERMOGRAPHIC LAYER COMPRISING AN ORGANIC COLLOID CARRIER HAVING DISPERSED THEREIN THE SILVER SALT OF BENZAMIDOXIME. 